(1) Field of Invention
The present invention relates to a water treatment system and, more particularly, to a water treatment system for simultaneous nitrification and denitrification.
(2) Description of Related Art
Water treatment, also referred to as sewage treatment, involves removing contaminants from wastewater and household sewage. Several processes are used to remove physical, chemical, and biological contaminants. Typically, a water treatment system utilizes three stages: primary, secondary, and tertiary treatment. Primary treatment involves containing the sewage to allow heavy solids to settle at the bottom of a basin, while oil, grease, and lighter solids float to the top. The liquid that remains after removal of the settled and floating materials is then subjected to a secondary treatment. The secondary treatment consists of removing dissolved and suspended biological matter using microorganisms (e.g., bacteria, protozoans). Finally, tertiary treatment is considered any further treatment of the water which improves the quality of the water prior to discharge to the receiving environment, such as disinfection.
One significant objective in secondary treatment is the reduction of nitrates, which are toxic and must be kept at low levels in accordance with the Environmental Protection Agency (EPA). Additionally, it is important to reduce ammonia levels during water treatment. The removal of nitrogen occurs through the biological oxidation of nitrogen from ammonia, or nitrification, followed by denitrification, which is the reduction of nitrate to nitrogen gas. Ammonia conversion generally occurs under aerobic conditions, while nitrate conversion generally occurs under anoxic/low oxygen conditions. In some cases, however, conversion of ammonia can also occur under anaerobic conditions. Nitrification itself is a two-step aerobic process, each step facilitated by a different type of bacteria. Denitrification generally requires anoxic conditions to encourage the appropriate biological communities to form and is facilitated by a wide diversity of bacteria. Currently, water treatment systems have separate aerobic and anoxic zones, or regions, in aeration basins for ammonia and nitrate conversion, respectively.
Thus, a continuing need exists for a cost-efficient water treatment system which serves the dual purpose of reducing ammonia and nitrate levels in water using a single device.